I’ve got a Technics SL-BD20D
bought it New in 1998. This thing has NEVER given me an issue until now. I bought a new belt and stylus recently, and that’s all well and good. However, the speed fluctuates slightly. I’ve adjusted from the bottom, but not long after you do that, it starts getting wavy again. I’ve never opened one of these up, and I’m assuming this is something minor, like cleaning something. Just don’t want to destroy this! Anyone else had this issue and know a good fix? Thanks so much!

The pitch control pot needs cleaning. A product like Caig Deoxit sprayed directly into the pot and the exercised back and forth to distribute the product will do the trick. It is best to take off the bottom of the turntable to access the pot. Spraying willy-nilly at the pitch control from the outside will not get the product where it needs to go.

Thank you! I will give this a try. I figured it’s probably pretty dirty in there. It’s a good 21 years old. Part of me would love something new, but the price tag has me saying, let’s keep this one going as long as possible! Ha.

If by "capstan", you mean spindle, there is the possibility that you have a gummed up spindle bearing. The spindle can be removed from the bearing well and both parts cleaned with alcohol and then fresh oil applied. There is probably a retaining nut or screw underneath that needs to be removed first. Some spindles have a small ball bearing on the bottom - be careful not to lose it. Apply several drops of oil into the bottom of the bearing well and a few drops to the spindle, then re-insert.